THE MOON — NASA's Artemis II mission is scheduled to lift off as early as 6:24 p.m. Eastern on Wednesday, sending four astronauts on the first crewed journey to the Moon since 1972. The mission aims to circle the Moon as a step toward a lunar landing in 2028, though the crew — three Americans and one Canadian — will not land on the surface.

The last humans to travel to the Moon were the crew of Apollo 17, the final mission of the Apollo program. Among them was Harrison Schmitt, now 90 years old, who left bootprints on the lunar surface during that December 1972 flight. Schmitt expects the Artemis II astronauts to see some of the same lunar features he observed more than five decades ago.

"Make sure that you've got your training down pat. Be ready for anything unexpected, but have a great time. Enjoy it." Schmitt, a former NASA astronaut, said in an interview, offering advice to the new crew. He also reflected on the nature of spaceflight: "Every day, every hour, every minute, is a new experience."

The Apollo 17 mission lasted nearly 13 days in space, with the astronauts spending more than three days on the lunar surface. During that time, they drove a lunar rover a total of about 19 miles and gathered geology samples totaling 243 pounds, which they brought back to Earth.

Additional Apollo missions were canceled after Apollo 17 as NASA's budget shrank in the 1970s. The agency prioritized work on space stations, and more than half a century passed without another crewed lunar voyage. Separately, China has announced plans to land astronauts on the Moon in 2030.

The Artemis II astronauts will be able to observe the Moon's far side more directly than astronauts in Apollo missions. Artemis II mission commander Reid Wiseman said in a media briefing, "It turns out there's about 60% of the far side, I think, that has never been seen by human eyes because of the lighting conditions." He added, "We've seen it in satellite photos, but humans have never, ever seen that before."

Apollo 8's flight around the Moon preceded the Apollo 11 landing, and NASA intends Artemis II to begin a new phase of lunar exploration.